Process for the extraction of the cellulose from vegetable fibers



by this process may be of any kind, such as UNHTEE STATS- aaraar oaarca.

IBENIAMINO CATALDI, 01F TURIN, ITALY, ASSIGNOE TO ALESSANDRO POMILIO, U1

NEW YORK, N. Y.

PROCESS FOR THE EXTRACTION OF THE CELLULOSE VEGETABLE FIBERS.

No Drawing.

To all whom it may concern:

a subject of the King of Italy, residing at Turin, Italy, have invented certain new and useful Improvements in Processes for the Extraction of the Cellulose from Ve etable Fibers; and I do hereby declare the ollowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to, make and use the same.

This invention relates to a process for the extraction of the cellulose from vegetable fibers by treatment with chlorine gas.

The vegetable fibres which can be treated for instance wood, cotton, straw, esparto grass, jute and the like.

According to the present invention the material to be treated, in its natural state if straw, esparto grass, jute, cotton and the like, or after removing the bark in the case of wood, is subjected to leaching in a digester, if required under heat, by means of an alkaline bath under heavy pressure, first hydraulic and then steam pressure. The material after having been brought in a suitable state of subdivision, if required, is placed in another digester lined with bricks or slabs of acid resisting materials and subjected to repeated successive treatments with chlorine gas alternating with water baths serving to cool the mass under treatment and to eliminate therefrom the hydrochloric acid formed by the action of the chlorine gas. These successive treatments with chlorine gas alternating with water baths being repeated until the temperature of the mass under treatment remain stationary. The fibers thus treated are washed with clean water and finally leached again in a slight alkaline bath similar to the first bath but under atmospheric pressure. In this last leaching bath the material under treatment will be freed from all encrusting ma-' terial or impurities and in this manner the cellulose is obtained which can be subsequently worked up in the usual manner.

The improved process may be performed as follows:

The material to be treated, in its natural state if it be straw, esparto grass, jute, cotton, and the like, or after removing the bark in the case of wood, is placed in an iron Specification of Letters .-?atent. Patenfigd Aug, 11, 11922 Application filed may 17, 1921. Serial No. 470,428. 7

digester containing, an alkaline leaching bath consisting, for instance, of a solution of from one to ten per cent of caustic soda or of lime water. In order toinsure the energetic and uniform action of the bath. upon the entire mass of the material to be treated, the process is carried on under pressure applied for instance by hydraulic means, by filling the digester to the top with the liquid and exerting upon it a pressure of 12 or 13 atmospheres, at the same time bringing the temperature of the bath up to 80 centigrade by any convenient means. After a certain length of'time the hydraulic pressure-is removed and steam at 4 or 5 atmospheres is introduced into the digester, thus raising the temperature of the bath to about that of the steam at this pressure. The duration of this leaching under pressure, which may be from 1 to 3 hours, will be more or less long according to the natureiof the materialto be treated.

After the leaching the liquid is run ofi from the digester and also the material under treatment is removed from the said digester and subjected to the action of chlorme gas.

Before the treatment with chlorine gas, in the case in which the material under treatment is wood, the said wood should be reduced to chips by means of any suitable machine. In the case. of straw, esparto grass, and the like they should, be first crushed by any suitable machine. and jute in general are already in favourable condition' for undergoing treatment with chlorine gas'without previous prep.- aration.

Now, the material under treatment is introduced. in a digester lined with briEcks or or slabs of acid resisting materials. the purpose of eliminating as completely as possible the water'of interposition and imbib ition from the material under treatment, a vacuum is produced in the digester in such a manner as to efi'ect the elimination gas is admitted slowly into the digester Cotton .ilm5 After the vacuum is produced, chlorine.

through suitable piping. This chlorine gas I lulose fibers, such as lignine, when the maing the final treatment with chlorine terial is wood. In consequence of this combination there is produced a considerable quantity of hydrochloric acid and there is developed a tendency to carbonize the said incrusted substances, owing to which, if the action of the chlorine is continued, the encrusted substances and in some measure the cellulose, would be destroyed, while the re mainder of the cellulose would be irremediably damaged by the hydrochloric acid thus formed. Therefore as soon as the tempera-- ture of the material" under treatment tends to rise perceptibly above 100 centigrade,the action of the chlorine gas is suspended and the chlorine is allowed to escape by displacement, by introducing into the digester wash- Ling water which carries off the hydrochloric acid and cools the mass.

The water is then drawn off, a vacuum is again created and the, chlorine gas admitted. If the temperature again rises excessively, the chlorine is again drawn off by displacement and the water introduced, and after the washing process a vacuum is once more created and the chlorine reintroduced; and so on, until on introducing the chlorine there is no longer any perceptible rise in the temperature. After being introduced the last time the chlorine gas may be made to act for from one to three hours or more, according to the nature of the material to be treated.

The number of successive treatments with chlorine gas. alternating with the washing process varies according to the quantity and nature of the incrusted substances, connecting the cellulose fibres to be extracted. Thus, in the case of wood four or five successive treatments with chlorine may be necessary, alternating with water baths, before reachas, during which-the temperature no longer rises perceptibly. In the case of straw, esparto grass and the like these treatments are generally limited to three, while in the case of cotton two are suflicient to obviate a ceptible rise in temperature.

- Afterthe last treatment with chlorine gas the latter is drawn off and the treated material is subjected to washing with clean water.- The treated material is then subper- Y pressure. By this renewed leaching the treated material is freed from all encrusted substances or impurities, which have been bath exactly the same as that employed for the first leaching but at the atmospheric.

'70 partly destroyed by the action of the chlorine state if straw, esparto grass, jute, cotton and the like, or after removing the bark in the case of wood, is subjected to leaching in a digester, if required under heat, by means of an alkaline bath under heavy pressure, first hydraulic and then steam pressure; whilst the said material, after having been brought in a suitable state of subdivision, if required, is placed in another digester lined with material imperviousto acid, and subjected to repeated successive treatments with chlorine gas alternating with Water baths, these baths serving to cool the mass under treatment and to eliminate therefrom the hydrochloric acid formed by the action of the chlorine gas; these successive treatments with chlorine gas alternating with water baths being repeated until the temperature of the mass under treatment remains stationary; while the material, after the final washing, is subjected as usually under, atmospheric pressure, to a final leaching with an alkaline bath exactly like the with water baths until the chlorine gas fails to raise the temperature of the mass and thereafter treating the mass with dilute alkali.

3. A process of deriving fibers from wood wherein the vegetable material is heated with dilute alkali under pressure, washed with water, comminuted, treated successively with chlorine gas and water until the treatment with'gas fails to raise the temperature of the mass,leached with dilute alkali, and finally bleached and washed.

4. "A' process for the extraction of cellulose from vegetable fibers comprising digesting the material in an alkali ne bath, subjecting it to successive treatments with chlorine gas whereby the temperature is caused to rise,

alternating suchtreatment with water baths 6. A process for the extraction of cellulose from vegetable fibers comprising digesting the material in an alkaline bath, subjecting it to successive treatments of chlorine gas whereby the temperature is caused to rise and alternating such treatments with water baths until the chlorine gas fails to raise the temperature of the mass.

, In testimony that I claim the foregoing as my invention I have signed my name.

BEN IAMIN O CATALDL 

